The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 199 04 891.6, filed on Feb. 6, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention relates to a calender, a system, and a method for reducing the humidity in a calender for webs of moisture-containing material, such as paper, with a housing having two side pieces and a roll stack, in which a space limited at least by the roll stack and the web is situated between the side pieces.
2. Discussion of Background Information
The space between the side pieces (or side walls) of a housing is customarily limited at one vertical or oblique face by the roll stack and is limited below by the floor of the workshop. If additional limits are formed by the web, for example, on the upper side and at the face opposite to the roll stack, a largely closed space is formed which is interchangeable with the ambient atmosphere only to a slight extent. This is particularly true for an in-line calender arranged near the drying cylinder of a paper machine, and also for an off-line calender with a closely adjacent unwinding device.
Since this limited space is incompletely connected to the ambient atmosphere, the air humidity inside it can rise due to the moisture of the paper web or of a steam moisturizing insert. As a result, the air in the limited space can become saturated, such that fog droplets form. In addition, the moisture can condense on the colder components, such as the housing, for example, which leads to the problem of corrosion. Moreover, there is a constant concern that droplets will fall onto the web from calender components, and this is undesirable. Additionally, the high humidity is also unpleasant for the service personnel who must enter this space.
The invention provides a calender of the initially described type with which the humidity problems are solved, while the limits of the space are maintained.
This is achieved according to the invention by a system which removes moisture from the air in the limited space by a number of methods, such as by introducing dry air into the limited space. A process which reduces the moisture in the limited space is also disclosed.
The embodiment of adding dry air has a two-fold effect. First, a slight over pressure is formed in the limited space, by which moist air is forced out into the environment via the still remaining openings. Secondly, the dry state of the fan air ensures that the humid atmosphere in the limited space does not reach the saturation state and thus the problem of the formation of droplets is avoided. The atmosphere is also made considerably more pleasant for the service personnel.
It is also possible to provide a heating device for the blast air. The blast air can therefore be fed in at a higher temperature and thus further improve the drying effect on the air in the limited space.
The invention contemplates using at least one moisture sensor and/or at least one temperature sensor arranged within the limited space, and a computer is provided that analyzes the values measured by the sensors and calculates a desired blast air state which is sufficient to avoid the saturation state in the limited space. Moreover, a computer-controlled system is provided for adjusting the state of blast air. By monitoring the atmosphere in the limited space and controlling or regulating the blast air state dependent on the values measured by the sensors, it is ensured that a saturation point of the moist air in the limited space is not reached.
For this purpose, the system may utilize a device such as a fan or other air exchange devices (i.e., air delivery or air removal devices) for adjusting the amount of blast air which enters the limited space. Moreover, a device such as a heating device can be used for adjusting the temperature of the blast air before it enters the limited space.
The invention also contemplates the utilization of a computer and a computer program for regulating, maintaining, and/or precisely controlling the air in the limited space at a level which is close to the saturation state. This ensures that the web, which borders the space and is transported through the space in the region of the roll stack, is not over dried.
The invention provides a calender for webs of moisture-containing material, including a housing having at least two side pieces and a roll stack located at least partially between the side pieces, wherein a space is formed by the roll stack and the web between the side pieces, and a fan positioned to blow dry air into the space. The material web may be a paper web. The dry air blown into the space may have a relative humidity which is lower than the relative humidity of the air disposed in the space. The calender may also include a heating device for heating the dry air. The calender may include at least one moisture sensor for measuring a humidity of the space and communicating the measurement to a computer. The calender may include at least one temperature sensor for measuring a temperature of the space and communicating the measurement to a computer. Moreover, the calender may include a computer which receives inputs from the at least one moisture sensor and the at least one temperature sensor for adjusting the humidity of the space. The calender may further include an air adjusting device for regulating one of the air velocity entering the space and the quantity the air entering the space. The air adjusting device may be a computer controlled fan adjusting motor. A temperature adjusting device for regulating the temperature of the dry air entering the space may also be utilized. The temperature adjusting device may be a computer controlled adjustable heating current regulator.
The invention may also utilize a computer program which manipulates input measurements from the at least one moisture sensor and the at least one temperature sensor and calculates outputs for regulating the humidity level within the space in the range of between approximately 75% and 95%.
According to another aspect of the invention, there is provided a system for regulating the humidity in a calender, the calender being used to treat a moisture-containing material web and including a housing having at least two side walls and a roll stack, the calender defining a space bounded at least by the roll stack, the web, and the at least two side walls, the system including a device for reducing the humidity of the space, wherein the humidity level in the space is reduced to a level which is below a saturation point. The device for reducing the humidity may be an air exchange device. The device for reducing the humidity may be a fan for removing air from the space. The device for reducing the humidity may also be a fan for blowing air into the space. The system may further include a heating device for heating the air. The system may use at least one moisture sensor for measuring a humidity in the space and communicating the measurement to a regulating device. The system may employ at least one temperature sensor for measuring a temperature in the space and communicating the measurement to a regulating device. The regulating device may be a computer which receives inputs from the at least one moisture and the at least one temperature sensors for adjusting the humidity of the space. The system may also provide for a an air adjusting device for regulating one of the air velocity entering the space and the quantity the air entering the space. The air adjusting device may be a computer controlled fan adjusting motor. The system can include a temperature adjusting device for regulating the temperature of the air entering the space. The temperature adjusting device may be a computer controlled adjustable heating current regulator. The system can utilize a computer program which manipulates input measurements from the at least one moisture sensor and the at least one temperature sensor and calculates outputs for regulating the humidity level within the space in the range of between approximately 75% and 95%.
According to still another aspect of the invention, there is provided a method of regulating the humidity in a calender, the calender being used to treat a moisture-containing material web and including a housing having at least two side walls and a roll stack, the calender defining a space bounded at least by the roll stack, the web, and the at least two side walls, the method including reducing the humidity of the space, wherein the humidity level in the space is reduced to a level which is below a saturation point. The reducing may include exchanging the air within the space with an air exchange device. The reducing may include introducing air to the space using a fan. The reducing may include removing air to the space using an exhaust fan. The method may provide for introducing air to the space using a fan. The method may include measuring the humidity in the space with at least one sensor. The method may also include regulating the humidity of the space using a control device which receives inputs from the at least one sensor. The method may provide for regulating the humidity of the space using a regulating device which receives inputs from the at least one moisture sensor. The method may employ regulating the humidity of the space using a control device which receives inputs from the at least one temperature sensor. The regulating may include maintaining the humidity in the space in the range of between approximately 75% and 95%.
The invention also contemplates a system for regulating the humidity in a calender, the calender being used to treat a moisture-containing material web and including a housing having at least two side walls and a roll stack, the calender defining a space bounded at least by the roll stack, the web, and the at least two side walls, the system including a device for reducing the humidity of the space, at least one moisture sensor disposed within the space, at least one temperature sensor disposed within the space, a control device for receiving inputs from the at least one moisture sensor and the at least one temperature sensor, wherein the control device controls the device for reducing the humidity so as to regulate the humidity level in the space to a point which is below a saturation point.
The invention further contemplates a method of regulating the humidity in a calender, the calender being used to treat a moisture-containing material web and including a housing having at least two side walls and a roll stack, the calender defining a space bounded at least by the roll stack, the web, and the at least two side walls, the method including measuring the humidity within the space with at least one moisture sensor, measuring the temperature within the space with at least one temperature sensor, comparing the humidity of the space to a desired value in a range using a computer which receives inputs from the at least one moisture sensor and the at least one temperature sensor, and regulating the humidity of the space to the desired value, wherein the humidity level in the space is reduced to a level which is within the range of between approximately 75% and 95%.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.